I've seen some strange behaviour from the Steam client during a game download after resuming the system from suspense.

On the first occasion, the download didn't resume, and the status line at the bottom of the window reported "No connection". I checked a few pages in Chrome, and my connection was OK. I tried pausing and resuming the download (no change). I tried disconnecting and reconnecting my WiFi (also no change). Re-starting the Steam client worked, the download resumed.

The second occasion was identical, except the the status line indicated 1 download (although nothing was actually happening).

On the third occasion, the download has resumed after suspense, but the status line says "NO CONNECTION" again.